Ribaxamase Protects Gut Microbiome, Cuts Opportunistic C. diff Risk

Ribaxamase is designed to be administered with IV beta-lactam antibiotics and remain localized in the intestine

This article is written live from ID Week 2017 Annual Meeting in San Diego, CA. MPR will be reporting news on the latest findings from leading experts in infectious diseases. Check back for more news from IDWeek 2017.

SAN DIEGO—Ribaxamase is associated with reduced risk for new, opportunistic Clostridium difficile infections (CDI) in hospital patients, according to findings from a multinational, double-blind, placebo-controlled Phase 2b study presented at IDWeek 2017.

“These data support that ribaxamase can maintain the balance of the gut microbiome and thereby prevent opportunistic infections like CDI during IV beta-lactam treatment,” said lead study author John Kokai-Kun, PhD, of Synthetic Biologics, Inc., Rockville, MD.

“Ribaxamase also protected the diversity of the gut microbiome and reduced the emergence of antibiotic resistance in ceftriaxone-treated patients,” he said.

CDI represent an “urgent threat” but there are no FDA-approved drugs or vaccines to prevent infections, Dr. Kokai-Kun noted.

“SYN-004 (ribaxamase) is a beta-lactamase designed to be orally administered with IV beta-lactam antibiotics and remain localized in the intestine to degrade antibiotics excreted into the intestine,” he said. “This is expected to protect the gut microbiome from disruption thus preventing deleterious effects including, CDI, colonization by opportunistic pathogens and emergence of antibiotic resistance in the gut microbiome.”

“Ribaxamase was well tolerated and not systemically absorbed in Phase 1 studies and efficiently degraded ceftriaxone excreted into the human intestine while not altering the plasma pharmacokinetics of ceftriaxone in Phase 2a studies,” he told the IDWeek audience.

Data from 412 patients (man age 70 years) in the intention-to-treat population “enriched for higher risk for CDI” were hospitalized for ≥5 days of IV ceftriaxone for treatment lower respiratory tract infections,” Dr. Kokai-Kun said. Patients were randomly assigned 1:1 to receive oral ribaxamase 150mg four times daily or placebo during IV ceftriaxone treatment and for an additional 72 hours.

“Fecal samples were collected at pre-specified points for determination of colonization by opportunistic pathogens and to examine changes in the gut microbiome,” Dr Kokai-Kun said. Patients were monitored for 6 weeks for CDI, defined as diarrhea plus the presence of C. difficile toxin.

Study participants saw a 71% relative risk reduction in CDI (P=0.045) and a statistically significant 44% relative risk reduction in new colonization by vancomycin-resistant enterococci (P=0.0002). Moreover, the respiratory infection was cleared in ~99% of cases demonstrating that concomitant ribaxamase did not impact the cure rate of ceftriaxone.

For continuous infectious disease news coverage from the IDWeek 2017, check back to MPR'sIDWeek page for the latest updates.